Aluminium oxide, properties, preparation, chemical reactions

Aluminium oxide, properties, preparation, chemical reactions.

 

 

Aluminium oxide is an inorganic substance has the chemical formula Al2O3.

 

Brief characteristics of aluminum oxide

Modification of aluminum oxide

Physical properties of aluminum oxide

Obtaining aluminum oxide

Chemical properties of aluminum oxide

The chemical reaction of aluminum oxide

The application and use of aluminum oxide

 


Brief description of alumina:

Aluminium oxide is an inorganic substance, which is colorless.

Aluminium oxide contains three atoms of oxygen and two atoms of aluminium.

The chemical formula of aluminium oxide Al2O3.

In nature it is found as alumina and corundum.

Insoluble in water.

Amphoteric oxide. Shows depending on conditions either basic or acidic properties. Their chemical properties manifests being heated to a high temperature of about 1000 OS.

 

Modification of aluminum oxide:

Known crystalline modifications of aluminum oxide: α-Al2O3, θ-Al2O3, γ-Al2O3, κ-Al2O3, η-Al2O3, χ-Al2O3.

Modification of aluminum oxide have different densities:

α-Al2O3 – 3,99 g/cm3,

θ-Al2O3 to 3.61 g/cm3,

γ-Al2O3 – 3.68 g/cm3,

κ-Al2O3 – 3,77 g/cm3.

α-modification of aluminum oxide is the only thermodynamically stable form of Al2O3.

 

Physical properties of aluminum oxide*:

Parameter name: Value:
Chemical formula Al2O3
Synonyms and foreign names aluminum oxide α-form (English).

corundum (English).

aluminum oxide α-form (Rus.)

corundum (Rus.)

The type of substance. inorganic
Appearance a colorless trigonal crystals
Color because of the impurities of aluminum oxide, as a mineral, can be painted in different colors
Taste —**
The smell
Aggregate state (at 20 °C and atmospheric pressure of 1 ATM.) solid
Density (state of matter – solid, at 20 °C), kg/m3 3990
Density (state of matter – solid, at 20 °C) g/cm3 3,99
Boiling point, °C 3530
Melting point, °C 2050
Molar mass, g/mol 101,96
Hardness on the Mohs scale 9

Note:

* aluminum oxide in α-form.

** — no data.

 

Obtaining of aluminum oxide:

Aluminium oxide obtained by reduction with aluminium metals from their oxides: chromium, molybdenum, tungsten, vanadium , etc. (metallothermy).

It is obtained the following metallotrejderskih reactions:

Cr2O3 + 2Al → Al2O3 + 2Cr (t = 800 oC);

3CuO + 2Al → Al2O3 + 3Cu (t = 1000-1100 oC), etc.

 

Chemical properties of aluminum oxide. The chemical reaction of aluminum oxide:

Aluminum oxide refers to amphoteric oxides.

Chemical properties of aluminum oxide similar to the properties of amphoteric oxides of other metals. So it is characterized by the following chemical reactions:

1. the reaction of aluminum oxide with aluminum:

4Al + Al2O3 ⇄ Al2О (t = 1450 °C).

The reaction produces aluminum oxide.

2. the reaction of aluminum oxide with carbon:

2Al2O3 + 9C → 2Al4С3 + 6СО (t = 1800 °C).

The reaction produced a salt – carbide aluminium oxide and carbon.

3. the reaction of aluminum oxide, carbon, and nitrogen:

Al2O3 + 3C + N2 → 2AlN + 3СО (t = 1600-1800 °C).

The reaction produced a salt – aluminum nitride and carbon monoxide.

4. the reaction of aluminum oxide with the sodium oxide:

Na2O + Al2O3 → 2NaAlО2 (t = 2000 °C).

In the reaction, the formed salt is sodium aluminate.

5. the reaction of aluminum oxide with potassium oxide:

K2O + Al2O3 → 2KAlО2 (t = 1000 °C).

In the reaction, the formed salt is potassium aluminate.

6. the reaction of aluminum oxide with magnesium oxide:

MgO + Al2O3 → MgAl2О4 (t = 1600 °C).

The reaction produced a salt of magnesium aluminate (spinel).

7. the reaction of aluminum oxide with calcium oxide:

CaO + Al2O3 → Ca(AlО2)2 (t = 1200-1300 °C).

In the reaction, the formed salt is calcium aluminate.

8. the reaction of aluminum oxide with the oxide of nitrogen:

Al2O3 + 3N2О5 → 2Al(NO3)3 (t = 35-40 °C).

In the reaction, the formed salt – the nitrate of aluminium.

9. the reaction of aluminum oxide with the oxide of silicon:

Al2O3 + SiO2 → Al2SiО5.

The reaction produced a salt – aluminum silicate. The reaction takes place in sintering of the reaction mixture.

10. the reaction of aluminium oxide with sodium hydroxide:

Al2O3 + 2NaOH → 2NaAlO2 + H2O (t = 900-1100 oC).

The fusion of aluminum oxide with dry sodium hydroxide. In the reaction, the formed salt is sodium aluminate and water.

11. the reaction of aluminum oxide with potassium hydroxide:

Al2O3 + 2KOH → 2KAlO2 + H2O (t = 900-1100 oC).

The fusion of aluminum oxide with dry potassium hydroxide. In the reaction, the formed salt is potassium aluminate and water.

12. the reaction of aluminium oxide with sodium carbonate:

Al2O3 + Na2СO3 → 2NaAlO2 + CO2 (t = 1000-1200 oC).

The reaction forms a salt with sodium aluminate and carbon dioxide.

13. the reaction of aluminum oxide with hydrofluoric acid:

Al2O3 + 6HF → 2AlF3 + 3H2O (t = 450-600 oC).

As a result of chemical reactions obtained salt – aluminum fluoride and water.

14. the reaction of aluminum oxide with nitric acid:

Al2O3 + 6HNO3 → 2Al(NO3)2 + 3H2O.

As a result of chemical reaction it turns out salt is aluminium nitrate and water.

Similarly, are the reaction of aluminum oxide with other acids.

15. the reaction of aluminum oxide with hydrogen bromide (bromoderma):

Al2O3 + 6HBr → 2AlBr3 + 3H2O.

As a result of chemical reactions obtained salt – bromide of aluminum and water.

16. the reaction of aluminum oxide with yodovidona:

Al 2 o 3 + 6HI → 2AlI3 + 3H2O.

As a result of chemical reactions obtained salt – iodide of aluminum and water.

17. the reaction of aluminium oxide with ammonia:

Al2O3 + 2NH3 → 2AlN + 3H2O (t = 1000 oC).

As a result of chemical reactions obtained salt – aluminum nitride and water.

18. the reaction of the electrolysis of aluminium oxide:

2Al2O3 → 4Al + 3О2 (t = 900 oC).

The electrolysis is carried out in the melt. The chemical reaction turns the aluminum and oxygen.

 

The application and use of aluminum oxide:

Aluminium oxide used for the production of aluminium powder for refractory, chemically resistant and abrasive materials, in the form of crystals, for fabrication of lasers and synthetic gemstones (rubies, sapphires, etc.), painted with admixtures of oxides of other metals.

 

Note: © Photo //www.pexels.com, //pixabay.com